Rich air fuel mix problem

Heads up. I have a problem with "rich" fuel trims, both short and long.

Background: I had elected to replace all of the emission-related sensors (MAP, ECT, IAT, etc) and fuel-air mix controllers (Intake Air Control Valve, Throttle Position sensor, Evap purge) that I could do myself.

In the precess of replacement I found a broken o-ring on the MAP sensor, which might explain the PCM pumping extra fuel and causing the "rich" mix.

I bought a new MAP sensor from AMZN and put it in, o-ring properly seated. Still suffering a "rich" mix condition. LTFT1 > 14.0 LTFT2 > 20.0.

Went back and reviewed parts ordered from AMZN, and thanks to their incorrect "fitment" feature, I found out that I bought the wrong MAP.

I am now waiting for the arrival of the correct part and will update this after installation and testing.

AMZN fitment disinformation: 56041018AB
Correct MOPAR part: 68002763AA

Look here (or similar elsewhere) for the correct MAP fitment: https://www.quadratec.com/products/55122_2005.htm


My own fault for trusting AMZN and their sponsored Chinese Supply Chain

dtennes said:

Heads up. I have a problem with "rich" fuel trims, both short and long.

Background: I had elected to replace all of the emission-related sensors (MAP, ECT, IAT, etc) and fuel-air mix controllers (Intake Air Control Valve, Throttle Position sensor, Evap purge) that I could do myself.

In the precess of replacement I found a broken o-ring on the MAP sensor, which might explain the PCM pumping extra fuel and causing the "rich" mix.

I bought a new MAP sensor from AMZN and put it in, o-ring properly seated. Still suffering a "rich" mix condition. LTFT1 > 14.0 LTFT2 > 20.0.

Went back and reviewed parts ordered from AMZN, and thanks to their incorrect "fitment" feature, I found out that I bought the wrong MAP.

I am now waiting for the arrival of the correct part and will update this after installation and testing.

AMZN fitment disinformation: 56041018AB
Correct MOPAR part: 68002763AA

Look here (or similar elsewhere) for the correct MAP fitment: https://www.quadratec.com/products/55122_2005.htm


My own fault for trusting AMZN and their sponsored Chinese Supply Chain

Click to expand...

I to bought a MAP sensor from Amazon, I always check package to see if part is old or new? I have problems with Amazon, I buy a lot of part from rockauto!

Installed the "correct" MAP #68002763AA, and it seems to have partially improved the fuel trim. I had unstable o2 sensor readings prior to MAP replacement were sticking between .07 and .65 V, with 1 sensor occasionally hitting .8... and my understanding is that its supposed to fluxuate between .1 and .9

Now 3 out of 4 o2 sensors are fluxuating between .1 and .85.

I think I may have a bad downstream o2 sensor and will be replacing that soon.

dtennes said:

Heads up. I have a problem with "rich" fuel trims, both short and long.

Background: I had elected to replace all of the emission-related sensors (MAP, ECT, IAT, etc) and fuel-air mix controllers (Intake Air Control Valve, Throttle Position sensor, Evap purge) that I could do myself.

In the precess of replacement I found a broken o-ring on the MAP sensor, which might explain the PCM pumping extra fuel and causing the "rich" mix.

I bought a new MAP sensor from AMZN and put it in, o-ring properly seated. Still suffering a "rich" mix condition. LTFT1 > 14.0 LTFT2 > 20.0.

Went back and reviewed parts ordered from AMZN, and thanks to their incorrect "fitment" feature, I found out that I bought the wrong MAP.

I am now waiting for the arrival of the correct part and will update this after installation and testing.

AMZN fitment disinformation: 56041018AB
Correct MOPAR part: 68002763AA

Look here (or similar elsewhere) for the correct MAP fitment: https://www.quadratec.com/products/55122_2005.htm


My own fault for trusting AMZN and their sponsored Chinese Supply Chain

Click to expand...

A thought! The cruise control is vacuum and line is connected under the coolant resivor with vacuum line controlling the a/c and heat positions, the line connects to the back of the intake manifold (maybe crack in line some where (check)

The downstreams usually don't have any effect on the air/fuel mix.

What do the short and long terms look like now at idle?

Xterra4x4 said:

A thought! The cruise control is vacuum and line is connected under the coolant resivor with vacuum line controlling the a/c and heat positions, the line connects to the back of the intake manifold (maybe crack in line some where (check)

Click to expand...

A very interesting thought, because I have what looks like a "rogue vacuum line" that has an end with some sort of weird white-plastic-breather plug stuck in it. The garage said it was "a transmission breather line" but I've been to the salvage yard a few times looking at 2003 3.7L intact drive trains, and I cannot find any similarity between this "dangler" and what's sitting intact in the yards.

I will take a pic and attach this morning.

***Self-admitted disinformation*** Problem solved. Spark plug gapped too tight. Was .034 and it should have been .044. Not enough spark to fully combust.

The truth is:
1. The underlying problem was *only parrtially due to* the plug gap set at .034 (which I found one reference to as being manufacturer spec somewhere but I'll die a happy man if I can ever find it again)
2. The true problem was mismatched gaps, 1 plug was .034 (set by mechanic) while the other 5 were at .044 (set by me), so the current suspicion is that the rough running and misfires was apparently due to the 1 plug sending a mismatched feedback signal back to the PCM. Once all plugs had the same gap, the PCM smoothed out the timing and now the KJ purrs at 7K RPM.

Takeaways:
3. I have since learned by trial and error that the acceptable gap could be anywhere between .034 and .044 (I have read that .044 is the appropriate setting for Jeep KJ 2002-2004 v6 3.7L according to NGK and other vendors for NGK Iridium plugs, and NGK web site also indicates that NGK Coppers are supposed to be set at, and are pregapped at .043 in the box)

>>>CORRECTION<<<

.044 is WRONG. Ignor the NGK spec and gap those copper plugs down to .040 !!! Yes, .044 will work but .040 gives much better engine performance. Plus a word of warning, just because the plug box says "pregapped to _____", that doesn't mean it actually is. Anyone can drop a box and accidentally bend the electrode. Always check the gap for accuracy.

>>>CORRECTION<<<


4. Overgapped plugs experience greater resistance, and .044 is pushing the limit on too much resistance meaning that sparking will start to become an issue as the electrode corrodes and the gap widens further over time. Artifacts will be sluggish and irregular gas pedal response, stalling, transmission gear slamming. The PCM talks to the TCM. They are synchronized, and each expects various feedback signals from the other. Garbled signals, crappy performance.
5. The smaller the gap the less resistance, so so you would think that the spark is more responsive and it is to an extent until it gets to closed which produces a dinky little spark that doesn't combust very well either.
6. Apparently, there is a sweet spot for a particular vehicle using specific plugs. Iridium and platinum plugs have pros and cons when compared with copper but you start to get into the whole trial and error exercise as you try to figure out what the appropriate gap should be with iridiums and plats. I tried iridium a while back and they were ok. Just ok.
7. The grey beards on this site are strong copper advocates, and since copper was original equipment, that has been the baseline for my trial and error experiments. Use NGK V-power copper. So what if you have to change them every 30K, they are the cheapest and closest to true OEM.
8. Getting to plugs #4 and #6 on a KJ is a PITA, so I didn't do too many gap variations. I pushed the gap out to .044 to start, but that hesitant response was still lurking around so I pulled the plugs back out and regapped down to .040. At .040 the engine is running quiet, smooth, and there's only a little trans punch but it is very infrequent, only happens between 1st and 2nd gear, and I have not yet determined the driving condition that causes it. When I find it I will update this post.
9. The temptation is to pull the plugs again and gap them down to .038 to see if the sporadic trans bang goes away, but the PCM and TCM are both "learning" machines that self-adjust over time, so before I do a regap again I will put a couple hundred miles on the plugs to see if the trans behavior corrects itself.

Good to know! In my Libby 2006 I don't touch the spark plugs, i mean I put them in with the same gap from manufacturer 0.04

0.040 is the correct gap !!! My reference to 0.044 is *not* correct and I edited my earlier reply to 0.040

dtennes said:

A very interesting thought, because I have what looks like a "rogue vacuum line" that has an end with some sort of weird white-plastic-breather plug stuck in it. The garage said it was "a transmission breather line" but I've been to the salvage yard a few times looking at 2003 3.7L intact drive trains, and I cannot find any similarity between this "dangler" and what's sitting intact in the yards.

I will take a pic and attach this morning.

Click to expand...

That rogue vacuum hose was in fact a transmission beather hose. It runs up from the auto trans, through the back of the engine compartment and ties off on the dipstick tube with a cable tie. There used to be a hose clip somewhere on the firewall but its long gone.

After everything was said and done, I replaced the upstream cat on the side with the trim problem and that further improved the trim problem.